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June 2, 1931. E. .w. MILLER FORMED TRUING TOOL FOR HELICOIDAL .ABI MDING WHEELS Filled Aug. 51, 1928 3 Sheets-Sheet l.

June 2, 1931. E; w. MILLER roman munze TOOL FOR HELICOIDAL ABRADING WHEELS Filed Aug. 31, 1928 s Sh eets-Sheet 2 E. W. MI LLER June 2, 1931.

I FORMED TRUING TOOL FOR HELICOIDAL ABRADING WHEELS Filed Aug. 51, 1928 3 Sheets-Sheet 3 Patented June 2, 19 31 UNITED STATES PATENT OFFICE EDWARD W. MILLER, OF SPRINGFIELD, VERMONT, ASSIGNOR TO THE FELLOWS GEAR SHAPER COMPANY, OF SPRINGFIELD, VERMONT, A CORPORATION OF VERMONT FORMED TRUING TOOL FOR HELICOIDA'L ABRADING- WHEELS Application filed August 81', 1928. SerialNo. 303,309.

number of difl'erent means for truing the helicoidal faces of such wheels, one of which forms the subject of the present invention and is disclosed in the following specification.

The abrading wheels which I have developed for thus finishing gears includes emery wheels and those of like nature, consisting of hard grit agglomerated with a binder, and metal laps to which loose abrasiveis supplied in the course of its action. Tools of both the types above mentioned require treatment of s milar nature to be he t true and accurate, but truing tools of speci cally diflerent characteristics may be used for different types of abrading wheels. For instance, diamonds, or minerals approximating the hardness of diamonds, are re uired for truing tools of the nature of emery w eels, but laps, which are commonly made of cast iron, may be trued by metal cutting tools 30 made of suitably hard and tough steel and alloys containing steel. The truing tool which forms the subject of this invention is particularly designed for truing such laps,

and in its embodiment for that purpose is made of a'tool steel com osition suitable for cutting cast iron. I shou (1 say, however, that I do not limit the protection which I claim to the truing tool made of such materials and suitable for truing metal laps only; for the novel principles of the truing tool maygbe embodied in tools of a structure and hardness truing tool having the characteristics above noted and further pointed out in the followlng specification and claims, and the combination of the same with means for operating it in conjunction with the abrading wheel.

In the drawings,"

Fig. 1 is a plan view of a gear finishing machine havin the new truing tool of the present invention applied thereto in substitution for the gear to be finished by the machine;

Fig. 2 isa side elevation of the machine, parts thereof being broken away and shown in section;

Fig. 3 is a fragmentary plan view on a larger scale showing the truing tool and a part of the abrading wheel in section;

Fig. 4 is a vertical section on line 4-4= of Fig. 3; v t 1ig. 5 is a perspective view of the truing oo v Like reference characters designate the same parts wherever they occur in all the figures.

The element or tool to be trued is an abrading wheel having a helical rib 11 of uniform pitch in projection on its axis, one face 12 of which is a helicoidal surface, the radial elements of which are perpendicular to the axis. For the purposes of this description, but without limitin intent, it may be assumed that the abra ing wheel is a lap made of cast iron or other suitable metal adapted to be armed or supplied with fine abrasive material. In using this wheel to finish the face of the ar teeth and generate involute curves in sur faces, it is mounted on a spindle 13 and rotated about its axis at a suitable speed. The work piece, a roughed out gear to be finished accurately to final form and dimensions, is mounted on a work spindle 14, and' is rotated at a rateand in the direction such that its base circle at the point nearest to the axis-of the abrading W eel moves in the same direction and at the same speed as the axial displacement of the rotatin helicoidal surface. The work piece is lace on the spindle with its medial plane, t at is,

the plane midway between its end faces, in coincidence with a radius of the helicoidal surface, or approximately so; and the machine is provided with adjustments by which the abrading wheel may be inclined or tilted so as to bring its helicoidal surface into coincidence with the longitudinal surface elements of the gear teeth being ground; and with other adjustments for moving the wheel in the axial direction, for moving the work toward and away fromthe axis of the Wheel, and for turning the work spindle through a small angle additional to its normal rotation so as to feed the work to the abrading wheel and determine the amount of stock to be removed thereby.

For the purposes of the adjustments above mentioned, the abrading wheel spindle is mounted in a head 15 which is adjustably supported on the machine base 16 with provision for movement. in the direction of the spindle 13, and is provided with a screw 17 and hand wheel 18 for adjusting it. work spindle is mounted in a work carriage 19 which is movable on guides on the base toward and away from the axis of the spindle 13. A screw 20 having a hand crank 21 is grovided for so adjusting this carriage.

imultaneous rotation is imparted to the spindles 13 and 14 from a belt pulley 22, or equivalent driver; the drivingv train to spindle 13 consisting of gears 23, 24 and 25, a shaft 26 and gears 27 and 28; and that to spindle 14 consisting of gears 29, 30, 31, 32,

a shaft 33, a spiral gear 24 splined to shaft 33, a spiral car 35 in mesh with 34 and secured to a s aft 36, a gear 37 also secured to shaft 36, and a ear 38 meshing with 37 and secured to spin le 14. A screw 39 is arranged to move the spiral car 34 endwise on shaft 33 and so turn the spindle 14 through a small angle additional to the rotation given it by the driving train. The details of a machine for this purpose having the characteristic above mentioned are fully disclosed and claimed in the copending application filed by me, to which reference is directed for a descri tion of features not described here.

y present purposesare satisfied by making it understood that the gear is rotated while being finished at a rate which causes the linear speed of its base circle to equal the rate of axial displacement of the helicoidal abrading surface, and that the abrading surface wipes constantly across the gear teeth with which it engages while its point of contact with the tooth shifts from root to point of the tooth, or vice versa. The abrading action takes place on a line tangent to the base circle and perpendicular to the radii of the helicoidal surface; or rather, since the gear has substantial thickness and the base circle is really a cylinder, the so-called line of action is really a plane. Preferably the tool and work are adjusted'so that the plane The of action intersects the helicoidal surface in order to distribute the wear on the latter rather than concentrate such wear on the outer edge.

Since the accuracy of the work produced by the machine depends on the accuracy of the abrading wheel, and the latter wears away appreciably in a relatively short time, particularly in the case of a lap, it becomes necessary to true or dress so much of the side face of the helical rib as acts upon the work, at frequent intervals. The part of the rib so trued must be restored to an exact helicoidal surface havin straight radial elements.

For'doing t is according to the present invention, I have provided a tool consisting of a single tooth 40 formed integral w1th, or otherwise suitably connected to, a carrier 41 which is adapted to be secured to the work spindle 14 in substitution for the ordinary work iece. The gear finishing machine as here shown is provided with a work holder 42 which is detachably fastened to the work.

spindle and by which a stem 43 is carried, such stem protruding above the holder and being adapted to pass through the central hole of the ear and having a threaded end to receive a 0 am ing nut 44. The trumg tool carrier 41, in this instance, is adapted to pass over the stem 43 and to be held fast by the same clamping nut. The width of the truin tool or tooth 40 is small enough to permit entrance of the tool between the turns of the helical rib 11, and it is provided at oneside with a cutting edge 45, the outline of which is an involute curve developed from a base circle corresponding to the normal itch to which it is desired to true the abradmg wheel. This base circle may be the same as that of the work piece to be finished by the abrading wheel, but is not'necessarily so, for a helicoidal surface which is perpendicular to its axis radially will generate an involute to any base circle which is 'ven a linear travel by rotation of the wor ual to the axial displacement of the helicoidal surface in a given len h of time; and, conversely, a cutt' too having an involute cutting edge dev o d from any base circle will generate a re ially straight helicoidal surface when rotated at the proper speed.

Hence, given definite speeds of rotation of the abrading wheel and work spindle, the truing tool must have its involute face developed from the base circle which has a linear displacement equal to the desired pitch of the hehcoidal surface durin one rotation of the abrading wheel. It will understood that in other respects the truing tool or tooth 40 is given the characteristics of a cutting tool which achieve the desired efiiciency in cutting, cast iron or any other material of which the abrading tool may be made.

In use the truing tool carrier is applied to the stud 43 and made fast, being located of the truing tool upto the helicoidal face of the'abrading wheel, and the machine is set in motion. As the helicoidal surface is displaced in the direction of its axis, the truing tool followsor precedes it in equal measure. Successive positions of the truing tool with successive complete rotations of the abrading wheel are shown by dotted lines in Fig. 3. The cutting contact ofthe truing tool proceeds from root to extremity of the cutting edge, or vice versa, according as the helix of the abrading tool is in one direction of pitch or the opposite direction. Operation of the adjusting screw 39 determines the amount of stock removed from the abrading wheel by the truing tool. The truing tool may be caused to make successive traverses across the abrading wheel and may be fed radially of the abrading wheel axis between traverses, in order to true a succession of zones and produce a flat surface (flat in the radial direction) of whatever width may be desired. Ordinarily it is necessary to have only a relatively narrow zone of the abradr ing wheel made straight and true, since the work to be finished will correspond very closely to the form of the truing tool. However, gears of larger diameter may be finished in the same machine, wherefore the wheel should be trued to a width sufficient for finishing larger gears without interference.

The principles of the tool herein shown and described are applicable to a formed truing element of any construction having a cutting edge, or a succession of cutting points sufdciently close together in projection on an involute curve, whether made of a material adapted to cut cast iron or other metals only, or of harder material which will dress emery wheels and the like.

The tool of this invention has the important advantage that it may be set up for use merely by being attached to the work spindle of the gear finishing machine, with a mini mum of labor and adjustment. However, it

is not merely an attachment'for a gear finishing machine, but on being applied to such a machine it converts the same into an organ-' ized helicoidal truing machine and becomes a part of such a machine. Evidently a tool of this character may be provided and used as a part of a machine designed exclusively for truing and to which the abrading wheel may be taken from the gear finishing machine to be trued. Hence the machine here illustrated may be taken as a representative of a class of gear truing machines within the scope of this invention and as typifying the principles of means essential to effect the desired action of the truing tool on the abrading wheel, regardless of any other functions which the machine may be adapted to perform. From this point of View, the truing tool becomes the operating tool of the machine, and the abrading wheel becomes the work piece the spindle 14,'which I have heretofore called the work spindle, becomes the tool or cutter spindle, and the spindle 13 becomes the work spindle.

What I claim and desire to secure by Lettcrs Patent is:

1. A machine for generating a helicoidal surface in an abrading wheel, comprising a tool having cutting points arranged in an involute curve developed from a base circle appropriate to the normal pitch desired to be produced in the helicoidal surface, means for rotating the abrading wheel about its axis, and means for rotating the truing tool about the axis of said base circle at a rate such that the linear travel of the base circle is equal to such normal pitch during the period of one rotation of the abrading wheel.

2. A means for generating and truing a helicoidal surface in an abrading, wheel, comprising means for supporting and rotating such wheel about the axisof its helicoidal surface, a formed truing tool having a succession of cutting points in an involute curve,

means for rotating said tool about the axis of the base circle of said involute curve, and means for effecting an adjusting relative movement retween the truing tool and the abraiding wl eel.

3. A means for generating and truing a helicoidal surface in an abrading wheel, comprising means for supporting and rotating such wheel about the axis of its helicoidal surface, a formed truing tool having a succession of cutting points in an involute curve, means for rotating said tool about the axis of the base circle of said involute curve, and means for effecting an angular adjustment of the abrading wheel additional to its normal rotational movement.

l. A formed tool for truing a helicoidal surface in an abrading wheel comprising a tooth having cutting points adapted to remove the stock of such abrading wheel, said points being arranged in an involute curve.

5. A formed truing tool for generating a helicoidal surface on a metal lapping tool comprising a tooth of material adapted to cut the material of the lapping tool, having a cutting edge in the outline of an involute curve.

6. A means for truing a helicoidal sur face with radial elements perpendicular to the axis of the helicoid in an abrading wheel, comprising means for supporting and rotating such wheel about the axis of its helicoidal surface, a formed truing tool having a succession of cutting points arranged in an lit= involute curve, means for rotating said tool about the axis of the base circle of said involute curve with a linear velocity at the base circle e ual to the axial displacement of the helicoi during rotation of the abrading wheel in a given period of time, and adjusting means or changing .the distance between the centers of: the abradin wheel and truing toolythe wheel and tool eing so arranged that the plane of rotation of the tool approximately coincides with an axial plane of the abrading wheel.

In testimony whereof I have affixed my signature. EDWARD W. MILLER. 

